The Curves viewThe area in the Timeline Editor window that shows the animation curves for Infinite clips or for Animation clips that have been converted from Infinite clips. The Curves view is similar to Curves mode in the Animation window. More info
See in Glossary provides the following methods for adding keys:
Right-click on an animation curveThe curve drawn between keys set for the same animatable property, at different frames or seconds. The position of the tangents and the selected interpolation mode for each key determines the shape of the animation curve. More info
See in Glossary and select Add Key. This method adds a key at the location of the Right-click.
Double-click on an animation curve. This method adds a key at the location of the Double-click.